A catalyst and a DPF (diesel particulate filter) are conventionally used to reduce an emission of CO (carbon monoxide), HC (hydrocarbon), NOx (nitrogen oxides) and PM (particulate matters) included in exhaust gas discharged from an automotive engine, more particularly a diesel engine. In the DPF, however, circulation of the exhaust gas is impaired as PM is collected and increased inside, and an exhaust resistance of the diesel engine is increased, thereby resulting in declines of fuel efficiency and outputs.
In recent years, there have been attempts to improve the above technical disadvantage, for example, removal of the collected PM through oxidation into gas (CO2) and reduction of the emission of such substances as PM by reforming the exhaust gas. A known approach for solving the problem is to use a plasma reactor in an exhaust gas purifying device including a catalyst. For example, in the exhaust gas purifying device for internal combustion engine described in Patent Document 1 includes at least a pair of discharge electrodes, wherein exhaust gas is flown between the discharge electrodes so that the exhaust gas is purified by discharge. In this device, a corrugated auxiliary electrode is disposed between the discharge electrodes so that protruding and recessed portions thereof extend along a direction of the exhaust gas flow in order to ensure a flow channel of the exhaust gas and improve discharge efficiency.    Patent Document 1: Japanese Unexamined Patent Publication No. 2001-9232